# OFDM based systems - reducing undesired radiation **URL:** \ **Category:** GNU Radio\ **Created:** [July 3, 2014, 1:26pm UTC](https://www.ruby-forum.com/t/ofdm-based-systems-reducing-undesired-radiation/230773 "2014-07-03T13:26:46Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [July 3, 2014, 1:26pm UTC](https://www.ruby-forum.com/t/ofdm-based-systems-reducing-undesired-radiation/230773/1 "2014-07-03T13:26:46Z")
Hello everyone, I am implementing a cognitive communication system inspired by GNURadio’s OFDM implementation and some custom designed spectrum sensing and management, medium access control, etc. In order to address OFDM’s undesired radiation issues, I am experimenting a technique reviewed in this nice post written by Tom Rondeau ([Peer Review of a DySPAN Paper — Rondeau Research](http://www.trondeau.com/blog/2014/4/23/peer-review-of-a-dyspan-paper.html)), but I’m having problems combining multiple IIR filters in series (eventually because of the resulting phase distortion). There are several techniques that can be found in the literature to address this issue, but I found this approach very interesting because of its simplicity. Eventually, my future goal is to implement some active cancellation sub-carrier style approach to mitigate non-contiguos radiation. I wonder how is the community addressing OFDM’s undesired radiation issues (non contiguous and out of the band). Best regards, Germano ---
**Author:** ![Germano](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/9fc29f/32.png) [@Germano](https://www.ruby-forum.com/u/Germano)\ **Post date:** [July 3, 2014, 8:13pm UTC](https://www.ruby-forum.com/t/ofdm-based-systems-reducing-undesired-radiation/230773/2 "2014-07-03T20:13:28Z")
I’m also working on OFDM thing, but got little progress now. Do you know how to start from existed OFDM code? THX!